Many different types of data storage systems exist and are being used to store data cartridges at known locations and to retrieve desired data cartridges so that data may be written to or read from the data cartridges. Such data storage systems are often referred to as "juke box" data storage systems, particulary if they can accommodate a large number of individual data cartridges.
A typical juke box data storage system may include one or more different types of cartridge receiving devices for holding the various data cartridges. For example, one type of cartridge receiving device may comprise a cartridge storage rack or "magazine" while another type of cartridge receiving device may comprise a cartridge read/write device. The cartridge storage racks or magazines serve to provide storage locations for the data cartridges and are commonly arranged so that they form one or more vertical stacks. The cartridge read/write device may be located adjacent the cartridge stack, although the cartridge read/write device may be positioned at any convenient location. The data storage system may also be provided with a cartridge access device for accessing the various data cartridges contained in the cartridge receiving devices and a positioning device for moving the cartridge access device among the cartridge receiving devices.
If a host computer system issues a request for data contained on a particular data cartridge, a control system associated with the data storage system actuates the positioning system to move the cartridge access device along the cartridge storage rack until the cartridge access device is positioned adjacent the desired data cartridge. The cartridge access device then removes the data cartridge from the cartridge storage rack and carries it to the cartridge read/write device. The cartridge access device inserts the selected data cartridge into the cartridge read/write device so that the host computer may thereafter read data from or write data to the data cartridge. After the read/write operation is complete, the cartridge access device may remove the data cartridge from the read/write device and return it to the appropriate location in the cartridge storage rack.
The cartridge access device typically used in such a data storage system may include a cartridge engaging assembly or "picker" which engages the selected data cartridge and withdraws it from the cartridge receiving device (e.g., either the cartridge storage rack or the cartridge read/write device, as the case may be). The picker may also insert the data cartridge into the cartridge receiving device.
A typical cartridge engaging device or "picker" may comprise a "thumb" assembly that is adapted to selectively engage and disengage the data cartridge. The thumb assembly is usually slidably mounted to the picker so that the thumb assembly can move toward and away from a cartridge access end of the picker. The picker may also include a thumb actuator system which moves the thumb assembly toward and away from the cartridge access end of the picker. For example, if it is desired to retrieve a data cartridge from a cartridge receiving device, the thumb actuator system moves the thumb assembly toward the cartridge access end of the picker so that the thumb assembly can engage or "grab" the data cartridge. The thumb actuator system may retract the thumb assembly and engaged data cartridge into the picker. If it is desired to load the data cartridge into the cartridge receiving device, then the thumb actuator moves the thumb assembly and data cartridge toward the cartridge access end of the picker, thus inserting the data cartridge into the cartridge receiving device.
A commonly used thumb actuator system utilizes a lead-screw drive system to move the thumb assembly toward and away from the cartridge access end of the picker. In such a system, the lead-screw may be mounted for rotation on the frame of the picker assembly and the thumb assembly may be mounted to the lead-screw via a suitable lead-screw nut. A motor drive assembly connected to the lead-screw is used to rotate the lead-screw which, in turn, causes the thumb assembly to move toward and away from the cartridge access end of the picker.
While such lead-screw drive systems are known and are being used, they are not without their disadvantages. For example, the lead-screw itself may be quite expensive and is generally supported in the picker frame by one or more ball bearings. Besides involving several relatively expensive components, such lead-screw actuator systems may also be difficult to assemble and align. Other problems may be associated with the motor drive assembly used to rotate the lead-screw. For example, the motor drive system is often coupled to the lead-screw via a drive belt and sprocket arrangement. Such a belt drive system typically involves providing one or more additional shafts to the frame assembly to support the various sprockets. Of course, the additional shafts require additional bearing support members, which adds to the overall parts count of the actuator system and may also provide additional assembly and/or alignment difficulties. Care must also be taken with such belt drive systems to ensure proper initial belt tension to avoid premature failure of the drive system.
Consequently, a need exists for a cartridge engaging assembly or picker that does not require a lead-screw drive system, which typically involves the use of relatively expensive components and may be difficult to assemble and/or align. Such lead-screw drive systems may also involve a high parts count, which tends to add to the overall cost of the thumb actuator system and may pose additional assembly and/or alignment problems. Still other advantages could be realized if such a picker assembly eliminated the need for belt drive systems, with all their associated disadvantages.